The present invention relates to a magnetic head assembly to be used in a floppy disc drive or the like, and more particularly to a magnetic head assembly having an arm rotatably supported to a carriage.
There will be described a conventional magnetic head assembly with reference to FIGS. 6 to 8. FIG. 6 is a sectional view of the magnetic head asembly. FIG. 7 is a plan view of an essential part showing a hinge portion between an arm and a carriage. FIG. 8 is a sectional view of the hinge portion. In FIGS. 7 and 8, some parts are omitted for the purpose of avoiding complicatedness.
Referring to these figures, the magnetic head assembly is mainly constituted of a carriage 20, an arm 21 and a leaf hinge spring 22, and is designed to be moved in a radial direction of a magnetic disc 24 along a guide shaft 23 by means of a pulse motor (not shown).
The carriage 20 includes a base material 25 therefor made of insulating synthetic resin, a head holder 26 mounted to a front end portion of the base material 25, a lower magnetic head 27 mounted to the head holder 26, a lead wire 28 derived from the lower magnetic head 27 and connected through a junction terminal 29 to an external lead wire 30, and a spacer 33 arranged on a rear end portion of the base material 25 and formed with push portions 34 projecting from a front end on both sides thereof, whereby recesses 35 are defined between the push portions 34 and the base material 25. Reference numerals 31 and 32 designate solders and adhesives for fixing the lead wire 30.
The arm 21 includes a base material 36 therefor made of insulating synthetic resin, a gimbal 37 of metallic spring thin plate mounted to a front end of the base material 36, an upper magnetic head supported to the gimbal 37, and a lead wire 39 derived from the upper magnetic head 38 and connected with a flexible print substrate 40 by means of the solder 31. The flexible print substrate 40 is connected with an external lead wire 41. The external lead wire 41 is fixed by the adhesives 32 at plural positions. The base material 36 is formed with substantially columnar support portions 42 at a rear end on both sides thereof. The support portions 42 have respective arcuately expanded portions 42a (See FIG. 8) inserted into the recesses 35 of the carriage 20 in such a manner as to directly abut against an upper surface of the base material 25 and be opposed to a lower surface of the push portions 34 with a small gap defined therebetween. Reference numeral 43 designates a lifting projection for upwardly moving the arm 21 which projection is provided on one side of the front end portion of the base material 36.
The leaf hinge spring 22 is formed of a metallic single plate such as a phosphor bronze plate or a stainless plate. One end of the leaf hinge spring 22 is embedded in the rear end portion at the center of the base material 36 of the arm 21, that is, in a part interposed between the pair of support portions 42 (See FIG. 7), while the other end is fixed through a fixture 44 to the carriage 20 by means of a screw 45. Reference numeral 46 designates a lock member for locking the screw 45. Reference numeral 47 designates a compression spring interposed between the fixture 44 and the base material 36 of the arm 21. The compression spring 47 acts to normally bias the arm 21 toward the carriage 20 side.
In operation, when the magnetic disc 24 is under an uninserted condition, the lifting projection 43 of the arm 21 is lifted by a lifting means (not shown) and rotated about the pair of support portions 42 to be restricted at a moving position as shown by an arrow in FIG. 6, wherein the upper magnetic head 38 is separated from the lower magnetic head 27 by a predetermined distance. When the magnetic disc 24 is inserted into the magnetic head assembly and then clamped, the restricted condition where the arm 21 is lifted by the lifting means is released in cooperation with the clamping, and the arm 21 is lowered by a resilient force of the compression spring 47. Then, the magnetic disc 24 is held by both the magnetic heads 27 and 38 to thereby permit reading and writing of information. In the holding operation of the magnetic disc 24, a relative positional relation between both the magnetic heads 27 and 38 is retained by the leaf hinge spring 22.
At the base portion of the arm 21, the arcuate portions 42a of the support portions 42 as a fulcrum are smoothly brought into contact with the carriage 20 to perform a hinging function on both sides of the leaf hinge spring 22. In the event that the arm 21 is rapidly lifted, the support portions 42 abuts against the push portions 34 so as not to generate an excess bending stress in the leaf hinge spring 22.
There are defined gaps A between the push portions 34 of the spacer 33 and the support portions 42 of the arm 21 so as not to restrict the rotation of the arm 21 upon lifting of same. Further, the gaps A function as a recess upon mounting of the arm 21 to the carriage 20 so that the upper magnetic head 38 mounted to the arm 21 may not abut against the lower magnetic head 27 mounted to the head holder 26 upon assembling.
However, in the aforementioned conventional device, existence of the gaps A causes oscillation of the arm 21 owing to external oscillation. As a result, the arm 21 is unexpectedly oscillated during recording and reproducing to generate off-track which has base influence upon recording and reproducing characteristics. Further, the gimbal 37 and the arm 21 are simultaneously oscillated because of sliding between the upper magnetic head 38 and the magnetic disc 24. Such oscillation causes generation of audible sound or socalled head noise.